The purine nucleus is an ubiquitous heterocyclic moiety present in a large number of biologically important molecules. The pyrrolo(2,3- d)pyrimidine ring (i.e., 7-deazapurine) is an analog of the purine system which has demonstrated a variety of significant biological effects. In particular the naturally occurring deazaadenosine nucleosidic antibiotics tubercidin, toyocamycin, and sangivamycin possess antitumor activity. In view of the considerable potential of this series of compounds, a systematic study to pinpoint the centers within the molecules which provide favorable activity would be extremely significant. Of concern in this proposal is the importace of the N-1 and N-3 nitrogen atoms of the deazapurine ring of these and related antibiotics. The overall ramifications of this study to the role of the purine nitrogens should be quite meaningful and will corroborate the minimal data available on this latter involvement. To achieve the objective under study here the technique of molecular modification and the monitoring of the accompanying effect of cancerous cells will be pursued. In this direction it is intended to synthesize pyrrolopyridine analogs of the antitumor deazapurine molecules previously known. For completeness preparation of representative 2'-,3'-, and 5'- monophosphates, 5'-triphosphates, 3',5'-cyclic monophosphates, 2'- deoxyribosides, and several dinucleotides will also be accomplished. Following biological evaluation against cancerous cells, it will be possible to discern the importance of the N-1 and N-3 atoms which, in turn, will allow a rational appraisal of the molecular basis for action and provide the impetus to commence the structural design of further molecules in this area of cancer chemotherapy.